A differential capacitive thin film hydrogen sensor

A compact, differential, hydrogen-specific sensor based on the lattice expansion of LaAl0.3Ni4.7 metal hydride thin films has been fabricated and characterized. Characterization of LaAl0.3Ni4.7 films performed using a capacitance dilatometer revealed that the lattice expansion was proportional to the partial pressure of H2 over the range 0.01–1.3 atm used in this experiment. The films were mechanically robust to cycling between vacuum and partial pressures of H2 up to 1.3 atm and were not poisoned by exposure to atmosphere's containing up to 24% carbon monoxide. A wafer level process has been established for the fabrication of the differential hydrogen sensor which includes both an active LaAl0.3Ni4.7 sensing capacitor and an inert Au reference capacitor. A minimum sensitivity of 400 ppm hydrogen is calculated for the differential device.